These goals will be accomplished within the framework of three existing NIH funded projects. The first project, entitled Behavioral Determinants of Opioid/Immune Interactions, provides an examination of Opioid-induced alterations of immune status with emphasis on the role of the central nervous system and pharmacological variables in these interactions. Specifically, the proposal is to conduct studies on the effects of acute and chronic Opioid administration on immune function, and identify the specific brain regions involved in those effects. The second project entitled Immune Alterations Mediated by conditioning, examines how conditioning processes can modulate immune status. This proposal involves examining the role of endogenous opiates in conditioned modulation of immune function. The third project, entitled Opioid-induced alterations of nitric oxide production by peripheral macrophages. This project will determine the subtype(s) of Opioid receptors involved in Opioid-induced alterations of nitric oxide production, and characterize the effect of Opioid administration on nitric oxide production in vivo. Collectively, these projects will provide important new information about Opioid- induced modulation of the immune system, and this award will enhance these investigations.